That sounds like a game for the Colecovision, but that doesn't quite match.

There was a game I remember playing 30 years ago on a BBC Micro called War and Peace.

Starts off by playing farmer in a feudal setting. After enough time you can go off to the crusades. Monochromatic amber.

As far as I can tell, the only evidence of its existence is in a Museum catelog.

No screenshots appear to exist. The developer is completely unknown. The only body that could be described as a publisher appears to be the education department of an Australian state government.

I can confirm they exist.

Source: I have made such games in the past.

If you restrict this to games that were commercially released, the most obscure one I've played is probably Centauri Alliance. It's like Bard's Tale, except in space, and it had some interesting ideas (technical skills, one playable race that can transform into different creatures), but also some issues (game interface is sluggish, have to press a key to see everyone's current health (especially a problem when radiation is involved), and many gameplay bugs (the worst being that charged psionic items use the wrong memory location when checking for/adjusting the charges remaining when used during battle).

It didn't help that this game was only released for the Apple 2 and Commodore 64 (no DOS version), and it was released when those computers were going out of style.

(As a side note: With the help of an emulator's debugging features, I managed to figure out how to fix that bug I mentioned, but there are still many others. On the other hand, I also figured out how to abuse that bug to get infininite uses of the game's (intended) second strongest attack spell (well, psionic power) early in the game.)

Since when was there a Commodore C116? Maybe you mean the Commodore 16 or 128?

The Commodore 116 was a variant of the C16 with a terrible rubber keyboard.See https://www.c64-wiki.com/wiki/Commodore_116

That keyboard was broken when my parents bought the machine in 1988 for 2,000 East German Marks and my step dad fixed it. My first own computer - pretty special in East Germany - and probably the reason I learned to code :-)

Probably Montezuma's Revenge or Monuments of Mars

Well, maybe the latter isn't that rare; seeing as it was released as freeware ages ago.

The game had simpler graphics, the background was probably black or another plain color, and the screen didn't scroll when you reached the end of it. I tried to make a screen combining the characters from the video you posted with the way I think the game may have looked like.

It even has a listing on Steam

The really obscure stuff vanishes without a trace.

How about this one? http://gad.art.pl/extra.php?page=sadistmain

Most obscure 1 I played is one someone here helped me find the name of. Presumed Guilty. Fun little adventure/detective game. It is Obscure enough that gamefabrique confused it with the game "Guilty" when posting screen shots.

There's a couple arcade games I have played in 1987 that I have never been able to track down, not even looking at every single MAME rom out there. They are so obscure that even I don't know the tiltes!

The game Smashing Pumpkins Into Small Piles Of Putrid Debris from the 1990s is pretty obscure. It is behind the lore of the id Software DOOM cheat code IDSPISPOPD.

The game Robinson which doesn't have a MobyGames page as well.

How to determine the obscurity level of a game?

Here's one, I only learned about from the ads in a games' magazine. I don't think I ever read a review of it at the time (1987).

"Echelon" for the C64.

It had a unique way of controlling: via "The Lip-Stik Plus Voice Activated Control Headset".

I falsely assumed I would get the headset with the game when I ordered it (should've read the desciption more carefully).

Of course, it turned out, you had to purchase the headset separately, and after buying the game, I hadn't the money left to do that. ;)

Luckily, you could also play it with KB/Joystick. Which is what I did.

http://cbmmuseum.kuto.de/echelon/title.jpg